Validating empty space in class validator

Question

I want to validate Address field, it may contains numbers or strings, but it should not accept continioues empty spaces

@IsAlphaNUmereic() Address: string;

i want that, Address can be numeric or alphabetic... but it should not accepts continues empty spaces

Markus · Answer 1 · 2022-05-12T11:41:10.557

33

An alternative solution without custom validation decorators would be:

@IsNotEmpty()
@Transform(({ value }: TransformFnParams) => value?.trim())
Address: string;

edited May 12 '22 at 11:41

answered Nov 15 '20 at 09:35

Markus

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the `.trim()` might crash if the `value` variable is null, undefined or any other type other than string. Should add an "optional chaining" like @razouq did in his answer below: https://stackoverflow.com/a/69595889/12056841 – Shani Kehati Feb 26 '22 at 21:28
1

Thanks @ShaniKehati, you are correct without it, it crashed. Please edit the answer – Cpp crusaders May 11 '22 at 07:20
@Markus what is the TransformFnParams ? where can I import that? – huykon225 May 25 '22 at 04:35
1

@huykon225 `import { TransformFnParams } from 'class-transformer';` – Markus May 26 '22 at 12:19
About usage of "optional chaining" necessity, is this still valid? I have tried with/without IsNotEmpty, if value is undefined, Transform cb never called? @ShaniKehati – Caner Sezgin Jun 24 '22 at 08:37
@CanerSezgin https://github.com/typestack/class-validator/blob/2ef8ff0f32be53e75dade2a0b86b158d87427176/src/decorator/common/IsNotEmpty.ts#L10 You might be correct, but, I won't rely on that- I would still make sure to check that the variable in `@Transform` decorator can be `trim`ed. **The best** would be to check `typeof value==="string"?value.trim():""` – Shani Kehati Jun 27 '22 at 06:49
@ShaniKehati your solution doesn't work with me – esraa Feb 19 '23 at 19:05
Hi, I added type-validation suggestion to the given answer, can I help you with something? What doesn't work? @esraa – Shani Kehati Feb 20 '23 at 13:03
I agree with Shani. In the case of a number, for example, optional chaining will not prevent the trim() method from being called on it, which will lead to a crash. – Yehezkel Jun 13 '23 at 07:21

eol · Answer 2 · 2020-01-30T12:23:04.280

Afaik there's no support for a "isNotBlank"-decorator, but you can just write one yourself:

import { registerDecorator, ValidationOptions } from "class-validator";

export function IsNotBlank(property: string, validationOptions?: ValidationOptions) {
    return function (object: Object, propertyName: string) {
        registerDecorator({
            name: "isNotBlank",
            target: object.constructor,
            propertyName: propertyName,
            constraints: [property],
            options: validationOptions,
            validator: {
                validate(value: any) {
                    return typeof value === "string" && value.trim().length > 0;
                }
            }
        });
    };
}

You would then add this custom validator to your existing one:

@IsNotBlank()
@IsAlphaNumeric()
Address: string;

Checkout https://github.com/typestack/class-validator#custom-validation-decorators for more information regarding custom validators.

that is what he has written, that you have to create your own decorator and register it with your code and then you can use it — Ankur Verma, Jan 16 '23 at 09:26

score 3 · Answer 3 · edited Nov 05 '21 at 05:48

3

@IsNotEmpty()
@Transform((({value}): string) => value?.trim())
Address: string;

destructure the 'value' after that you can trim it

edited Nov 05 '21 at 05:48

Spikatrix

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answered Oct 16 '21 at 13:09

razouq

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you shouldn't assign the `string` type to the `value` variable because it could be anything. Should just follow the `TransformFnParams` type. just like @Markus suggested in his answer above: https://stackoverflow.com/a/64842927/12056841 – Shani Kehati Feb 26 '22 at 21:24

score 2 · Answer 4 · answered Aug 01 '22 at 10:19

2

You can use the the @NotContains class validator. DTO should like this:

@IsAlphaNUmereic()
@NotContains(" ")
address: string

answered Aug 01 '22 at 10:19

ZinnieZee

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3

score 0 · Answer 5 · answered Feb 16 '23 at 06:42

Here is the best way to validate your key: Import the required properties:

import { IsNotEmpty,Length,NotContains } from "class-validator";
import { Transform } from 'class-transformer';
import { ApiProperty } from "@nestjs/swagger";

Create a class for the payload:

export class SomePayloadCheckDto {
  @ApiProperty({ required: true })
  @IsNotEmpty()
  @NotContains(" ")
  @Transform(({ value }) => value?.trim())
  @Length(3, 20)
  someString: string;
}

Validating empty space in class validator

5 Answers5